[GSBN] [nbne] Earth plaster and Cellulose

Mon Apr 29 03:36:50 UTC 2013

Thanks for your feedback Ian, nice to get your perspective.  Fortunately 
in this to case there is no push for a vapor barrier from the architect 
- a battle I've had to fight many times.  We follow a very similar 
protocol to yours involving lime wash, and are explicit in describing 
the function to clients as not only a sacrificial layer to protect 
erosion of the plaster, but a 'sealant' of sorts that reduces moisture 
absorption into the plaster while maintaining high vapor permeability.

This structure is a multi-occupant commercial building (cabin/lodge) at 
an institution, and a low-maintenance finish is a strong priority.  
This, coupled with the architect's unfamiliarity and general discomfort 
with the principles of plastered wall assemblies (not aesthetic, but 
plaster coupled to the interior of the assembly), directed the project 
towards cladding.  Ah well...

On a related note, I have a good friend in colleague in Halifax (Kim, 
maybe you know her, Annie Murphy?)  who has told me that they have all 
but entirely moved towards wood cladding over their SB buildings because 
the climatic pressures are too much for plaster when 'deferred 
maintenance' is a reality, it's interesting to hear how different 
regions approach the finishing of the same wall assembly - I appreciate 
that there are climate-responsive vernacular traditions emerging.

Cheers,
Jacob

Jacob Deva Racusin
New Frameworks Natural Building, LLC
P.O. Box 15, Montgomery, VT 05470
(802) 782-7783 (c)
(802) 326-2209 (h)
www.newframeworks.com
jacob at newframeworks.com

On 4/28/2013 6:01 PM, Ian Redfern wrote:
> Good morning Jacob,
>
> Thanks for the invitation to comment from this outreach of the straw 
> bale building network.
>     Here in northern New Zealand with a climate not too unlike the 
> lower new England states and certainly similar to Oregon and coastal 
> Washington State where we have sub cyclonic conditions with continuous 
> high humidity (80 -- 100%).
>
>     Over more than 15 years of designing natural (adobe and straw 
> bale) houses and observing the lime plaster putty based plasters, 
> renders and white washes on them -- the lime putty based products have 
> stood up fantastically to wind driven rain and shedding internal 
> humidity on straw bale and earthen walling !
>
>     Lime putty based white wash (simple lime putty and water   AND not 
> thick creamy stuff) is fantastic at healing any micro cracking that 
> may occur during the seasonal changes -- we specify an initial five 
> coat on the green render coat then annually (I have just redone 
> [render in parts and three coats of whitewash] on the exposed sections 
> of our adobe cottage after 6 or 7 years)
>
>     As said in an earlier thread the rogue element is in installing 
> any form of vapor barrier in the wall matrix -- the vapor needs to be 
> pulled to the outside and lifted off by the infinite atmosphere (we 
> express this as the drying effect of air movement around the building 
> (outside air movement reduces the water vapor [and other gasses] 
> partial pressure at the wall surface  which is why we purposefully 
> leave a rough textured surface)
>
>    I trust this is not too detailed -- it is better expanded on by 
> Straube and Burnett in their book "Building Science for Building 
> Enclosures"
>
> Cheers
>
> Ian
>
>     The timber framed houses we have designed and built use a 
> polyester insulation between the framing with a vapor permeable 
> building wrap then cavity battens (20mm =  3/4") behind the lime 
> plaster that is reinforced with a polypropylene expanded mesh, then 
> the 5 coats of whitewash =  reassurance to client, building regulator, 
> and contractor
> And still doing well after many years of coastal battering (this home 
> has generous eaves on the second story but the lower level receives 
> full force of wind driven rain)
>
> Description: Macintosh 
> HD:Users:ianredfern:Desktop:logo2.jpg*www.adobesouth.co.nz*
>
> 	
>
> Ian Redfern
> *Adobe South*
> *A:*    5 Lancewood Rise, Onerahi, Whangarei
> *P:*09 436 4040*M:* 027 490 2324
> *E:*ian at adobesouth.co.nz
>
>
> From: Jacob Racusin <buildnatural at googlemail.com 
> <mailto:buildnatural at googlemail.com>>
> Reply-To: Global Straw Building Network <GSBN at sustainablesources.com 
> <mailto:GSBN at sustainablesources.com>>
> Date: Sat, 27 Apr 2013 10:22:50 -0400
> To: Derek Stearns Roff <derek at unm.edu <mailto:derek at unm.edu>>, 
> "<nbne at lists.riseup.net <mailto:nbne at lists.riseup.net>>" 
> <nbne at lists.riseup.net <mailto:nbne at lists.riseup.net>>
> Cc: "<gsbn at sustainablesources.com 
> <mailto:gsbn at sustainablesources.com>>" <gsbn at sustainablesources.com 
> <mailto:gsbn at sustainablesources.com>>
> Subject: Re: [GSBN] [nbne] Earth plaster and Cellulose
>
> Great reference Derek. The inclusion of multiple coats of limewash 
> does a lot to limit bulk water absorption in the plaster, reducing the 
> "charge" of the reservoir cladding.
>
> Having met with the architect, I learned their chief concern is not 
> vapor drive, but wind-driven moisture through inevitable cracks in the 
> plaster bulk-loading water into the assembly. They cited hurricane 
> exposure as an extreme design condition, and the issue was less about 
> the cellulose and more about the location of the structural framing 
> (as opposed to a bale-wrapped timber frame). Certainly good arguments 
> for wood cladding, lord knows the storms are only getting stronger and 
> more frequent...
>
> Thanks to those who replied!
>
> Jacob
>
> Sent from my Windows Phone
> ------------------------------------------------------------------------
> From: Derek Stearns Roff
> Sent: 4/26/2013 5:55 PM
> To: <nbne at lists.riseup.net <mailto:nbne at lists.riseup.net>>; Jacob Deva 
> Racusin
> Cc: <gsbn at sustainablesources.com <mailto:gsbn at sustainablesources.com>>
> Subject: Re: [nbne] Earth plaster and Cellulose
>
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